 IVES 9 IVES Conference Series 9 Evolution of flavonols during Merlot winemaking processes

Evolution of flavonols during Merlot winemaking processes

Abstract

Aim: The phenomenon of quercetin precipitation in wine (flanovol haze), has been manifested for many years in several wine-producing regions, such as Italy, Australia, and New Zealand (Gambuti et al., 2020; Lanati, Marchi, & Cascio, 2014; Somers & Ziemelis, 1985). Due to the limited information related to the quercetin aglycone behavior and its precursors during wine production in New Zealand, this study aims to monitor the evolution of flavonols and other polyphenols during the commercial fermentation of Merlot grapes, using different fermentation conditions, and vineyard treatments.

Methods: Various trials evaluating sun exposure, winemaking practices, and winemaking process management were undertaken using Merlot grapes, commercial yeast cultures, potassium metabisulphite (20 g/hL), and nutrient supplementation with DYNASTART®-LAFFORT at 20 g/hL. Samples were taken through the winemaking stages, and the polyphenols were quantified using a reversed-phase HPLC method (Garrido-Bañuelos et al., 2019; Peng et al. 2002).

Results: Grapes with elevated amounts of flavonols glycosides produced wines with higher levels of flavonol glycosides and quercetin. Wines made from grapes with greater sun exposure ended up with more flavonol glycosides (89 mg/L) and quercetin (16 mg/L) than the wines elaborated from less exposed grapes (47 mg/L and 9.4 mg/L, respectively). Certain winemaking practices showed differences in quercetin content, for example using small fermentation (250 kg) (12 mg/L), and large fermentation (five tonnes) (28 mg/L). The data also indicates that tannins and total anthocyanins were present at 786 mg/L and 156 mg/L, respectively, for small-scale ferments, and at 888 mg/L and 363 mg/L, respectively, for large-scale ferments. In evaluating the winemaking process management, the ferment pumped over (largest fermentation volume) exhibited flavonol glycosides and quercetin at the highest concentration (91 mg/L and 20 mg/L, respectively), compared to the remaining treatments. PMS, enzyme, and PMS plus enzyme, additions lowered the concentration of the flavonols glycosides at the end of the winemaking process (37 mg/L, 42 mg/L, and 43 mg/L, respectively). It was seem that the PMS plus enzyme (15.6 mg/L) increase quecetin in wine when compared to the control, no additions, (12.6 mg/L). The wines treated with enzyme, PMS, and PMS plus enzyme, also had lower concentrations of anthocyanins (215 mg/L, 233 mg/L, and 238 mg/L, respectively) than the control (291 mg/L).

Conclusions

The study confirmed past research on the role of sun exposure in the formation of flavonols in Merlot grapes and wines. Fermentation size can improve the extraction of polyphenols into wine, and the enzyme additions can promote the hydrolysis of flavonol glycosides. In considering winemaking practices to lower flavonol content, the impact on remaining wine phenolics, of importance to wine colour and mouthfeel, also needs to be carefully evaluated.

DOI:

Publication date: September 14, 2021

Issue: Macrowine 2021

Type: Article

Authors

Cristian Hernandez

School of Chemistry University of Auckland,Paul KILMARTIN, School of Chemistry, University of Auckland Leandro DIAS, School of Food Science, University of Auckland Gianni FLEGO, Villa Maria Estate winery Rebecca DEED, School of Biological Sciences, University of Auckland

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Citation

An analytical framework to site-specifically study climate influence on grapevine involving the functional and Bayesian exploration of farm data time series synchronized using an eGDD thermal index

Climate influence on grapevine physiology is prevalent and this influence is only expected to increase with climate change. Although governed by a general determinism, climate influence on grapevine physiology may present variations according to the terroir. In addition, these site-specific differences are likely to be enhanced when climate influence is studied using farm data. Indeed, farm data integrate additional sources of variation such as a varying representativity of the conditions actually experienced in the field. Nevertheless, there is a real challenge in valuing farm data to enable grape growers to understand their own terroir and consequently adapt their practices to the local conditions. In such a context, this article proposes a framework to site-specifically study climate influence on grapevine physiology using farm data. It focuses on improving the analysis of time series of weather data. The analytical framework includes the synchronization of time series using site-specific thermal indices computed with an original method called Extended Growing Degree Days (eGDD). Synchronized time series are then analyzed using a Bayesian functional Linear regression with Sparse Steps functions (BLiSS) in order to detect site-specific periods of strong climate influence on yield development. The article focuses on temperature and rain influence on grape yield development as a case study. It uses data from three commercial vineyards respectively situated in the Bordeaux region (France), California (USA) and Israel. For all vineyards, common periods of climate influence on yield development were found. They corresponded to already known periods, for example around veraison of the year before harvest. However, the periods differed in their precise timing (e.g. before, around or after veraison), duration and correlation direction with yield. Other periods were found for only one or two vineyards and/or were not referred to in literature, for example during the winter before harvest.

Adaptability of grapevines to climate change: characterization of phenology and sugar accumulation of 50 varieties, under hot climate conditions

Climate is the major factor influencing the dynamics of the vegetative cycle and can determine the timing of phenological periods. Knowledge of the phenology of varieties, their chronological duration, and thermal requirements, allows not only for the better management of interventions in the vineyard, but also to predict the varieties’ behaviour in a scenario of climate change, giving the wine producer the possibility of selecting the grape varieties that are best adapted to the climatic conditions of a certain terroir. In 2014, Symington Family Estates, Vinhos, established two grape variety libraries in two different places with distinctive climate conditions (Douro Superior, and Cima Corgo), with the commitment of contributing to a deeper agronomic and oenological understanding of some grape varieties, in hot climate conditions. In these research vineyards are represented local varieties that are important in the regional and national viticulture, but also others that have over time been forgotten — as well as five international reference cultivars. From 2017 to 2021, phenological observations have been made three times a week, following a defined protocol, to determine the average dates of budbreak, flowering and veraison. With the climate data of each location, the thermal requirements of each variety and the chronological duration of each phase have been calculated. During maturation, berry samples have been gathered weekly to study the dynamics of sugar accumulation, between other parameters. The data was analysed applying phenological and sugar accumulation models available in literature. The results obtained show significant differences between the varieties over several parameters, from the chronological duration and thermal requirements to complete the various stages of development, to the differences between the two locations, confirming the influence of the climate on phenology and the stages of maturation, in these specific conditions.

VineyardFACE: Investigation of a moderate (+20%) increase of ambient CO2 level on berry ripening dynamics and fruit composition

Climate change and rising atmospheric carbon dioxide concentration is a concern for agriculture, including viticulture. Studies on elevated carbon dioxide have already been on grapevines, mainly taking place in greenhouses using potted plants or using field grown vines under higher CO2 enrichment, i.e. >650 ppm. The VineyardFACE, located at Hochschule Geisenheim University, is an open field Free Air CO2 Enrichment (FACE) experimental set-up designed to study the effects of elevated carbon dioxide using field grown vines (Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon). As the carbon dioxide fumigation started in 2014, the long term effects of elevated carbon dioxide treatment can be investigated on berry ripening parameters and fruit metabolic composition.
The present study aims to investigate the effect on fruit composition under a moderate increase (+20%; eCO2) of carbon dioxide concentration, as predicted for 2050 on both Riesling and Cabernet Sauvignon. Berry composition was determined for primary (sugars, organic acids, amino acids) and secondary metabolites (anthocyanins). Special focus was given on monitoring of berry diameter and ripening rates throughout three growing seasons. Compared to previous results of the early adaptative phase of the vines [1], our results show little effect of eCO2 treatment on primary metabolites composition in berries. However, total anthocyanins concentration in berry skin was lower for eCO2 treatment in 2020, although the ratio between anthocyanins derivatives did not differ.
[1] Wohlfahrt Y., Tittmann S., Schmidt D., Rauhut D., Honermeier B., Stoll M. (2020) The effect of elevated CO2 on berry development and bunch structure of Vitis vinifera L. cvs. Riesling and Cabernet Sauvignon. Applied Science Basel 10: 2486

Mesoclimate impact on Tannat in the Atlantic terroir of Uruguay

The study of climate is relevant as an element conditioning the typicity of a product, its quality and sustainability over the years. The grapevine development and growth and the final grape and wine composition are closely related to temperature, while climate components vary at mesoscale according to topography and/or proximity to large bodies of water. The objective of this work is to assess the mesoclimate of the Atlantic region of Uruguay and to determine the effect of topography and the ocean on temperature and consequently on Tannat grapevine behavior.

How can historical cultivars mitigate the effects of climate change?

IFV, INRAe and the national network “Partenaires de la Sélection Vigne” representing 37 organizations from the different wine regions, have been working increasingly closely over the last 2 decades towards the preservation of the French varietal patrimony. There are approximately 600 patrimonial varieties according to INRAe and SupAgro Montpellier experts, including ancient cultivars (400) and intravarietal crossbreeds obtained since the 19th century. In the context of a drastic reduction in such varieties from the mid 1980’s in favor of mainstream varieties, it was essential to carry out an inventory of old vines and vineyards. INRAe Vassal collection plays a key role here as it holds the largest diversity available, along with a rich bibliography and herbariums, offering us the opportunity to document and double check the identity of a cultivar, consolidating the expertise of ampelographers. The work is carried out in several stages, from verifying the existence of a variety in a small region, through to rehabilitation. During this session, the authors present the process that leads to the official registration of a variety. After this, IFV selection center takes over to initiate the process of selection and propagation. A specific focus within regions such as the Alps, Champagne and the South-West will provide details of the full procedure. Bia, Bouysselet, Chardonnay rose, Mecle and the aptly named Tardif, are some of the cultivars that have followed this procedure. Furthermore, a recent regulation established by INAO on “varieties of interest for adaptation purposes” might boost uptake by growers. Since 2006, 36 historical cultivars have been registered. Most of these have been neglected in the past due to late maturity, lack of sugar and high titratable acidity at harvest time. Such characteristics are today considered as positive qualities, not only in mitigation of the effects of climate change, but also as an opportunity for restoring diversity…